Actuators that include shape memory materials, such as shape memory alloys (SMAs) and shape memory polymers (SMPs), are generally light weight devices that can quickly expand or contract and generate significant forces when heated. Also, they can be programmed in any shapes and when heated they can generate large amount of force. In order for such actuators to return to their original positions by contraction, the SMAs/SMPs should be cooled, which may limit their use in certain applications. Some implementations of SMAs/SMPs in actuators use return springs, for example, to physically return the actuators to their original positions, but the use of return springs may increase the energy consumption of such actuators by at least 100% and do not improve the bandwidths of the actuators above 1 Hz. Although some actuators with SMAs or SMPs have been designed with attempts to improve natural convection to cool the SMAs/SMPs so that they return to their original positions, such designs are not very efficient, are relatively bulky, and have complicated designs.